Endoscope fitted with a window covering a light guide and an image transmitter

ABSTRACT

A rigid endoscope optics, comprising an outer tube ( 1 ) of which the distal aperture is closed by a window ( 2 ) affixed to it in sealed manner, said outer tube enclosing an image transmitter ( 4, 5 ) running through it and a light pipe ( 6 ) running parallel to said transmitter, said transmitter and pipe being configured by their distal ends ( 5, 7 ) looking and. radiating resp. through the window, the light-pipe being cross-sectionally separated from the image transmitter&#39;s cross-section at least in the region subtended between their distal ends and the window by an optically opaque partition ( 3 ) that rests by its distal edge against the window, is characterized in that the distal end of the partition ( 3 ) rests by means of an elastic and opaque insert ( 9 ) against the window ( 2 ).

[0001] The present invention relates to an endoscope optics of the kind defined in the preamble of claim 1.

[0002] Such an endoscope optics is known from the German patent document 195 25 995C1.

[0003] The endoscope optics of this kind offer the substantial advantage of the window being directly affixed in the outer tube of which it covers the full cross-section and being perfectly sealed off for instance by soldering, and accordingly of hermetically sealing the entire inside space containing the susceptible optical surfaces. Such a design reliably secures the optics against invading liquids and vapors, in particular under the critical conditions of steam autoclaving to sterilize endoscope optics for medical applications.

[0004] Optics of such kind, namely fitted with a window jointly covering the cross-sectional zone of the light pipe and the image transmitter, incur however the problem that the light is irradiated from the exit of the light pipe into the distal entry end of the image transmitter. Such light radiation entails interfering light reflections in the image. As already discussed in the above cited document, light entering the window is reflected in it and may exit toward the light pipe. As a result said document assumes that direct light penetration from the light pipe into the image transmitter no longer can take place in front of the window because being precluded by a partition.

[0005] Now it has been discovered that such an assumption is unwarranted. To a substantially interfering degree, light also passes through a gap between the distal edge of the partition and the window.

[0006] The objective of the present invention is to preclude the light penetration otherwise taking place already in front of the window.

[0007] This problem is solved by the features of claim 1.

[0008] The present invention is based on the insight that the known design of the above cited kind, wherein a partition internally abuts the window, is unable to prevent light penetration inside this window. The partition and the outer tube undergo different thermal expansions. It must be borne in mind in this respect that endoscope optics of the above kind are subjected to high temperature fluctuations. When typically used in medical applications, temperature changes in the first place arise between room and body temperatures. During conventional steam sterilization, the said optics is raised from room temperature to above 120° C. and then is cooled to room temperature again. If the partition is designed to always abut the window in light-tight manner, then, in the presence of longitudinal thermal expansion, said partition shall excessively stress the window and break it. If the said partition's length is selected so that it cannot pressurize the window, then perforce a gap shall be subtended between said partition's distal wall and the window, and this gap may transmit light. Accordingly the invention provides that the distal edge of the partition rest by means of an elastic, light-tight insert against the window. Said insert assures optically sealing the gap under all conditions of partition expansion, and this without unduly stressing said window. Accordingly this design reliably prevents light from entering the image transmitter within the window, and this in the absence of danger to the window. Tests have shown that as a result the essential portion of the interfering light penetration shall be precluded. An optics of the invention is applicable without suffering from significant light reflections. The invention also applies to all design variations, that is in particular to endoscope optics with optic fiber cables as light pipes and to image transmitters both in the form of optic fiber cables and in the form of systems of relay lens elements. The partition may be configured at arbitrary cross-sections between the two cross-sectional zones, in particular in conventional manner as a system tube enclosing the image transmitter. Advantageously the partition shall run not only across the range between the distal ends of light pipe and image transmitter and the window, but also over the essential length of the light pipe in order to avert also light penetration in the rear zone.

[0009] The spacer illustratively may be in the form of an adhesive connection of a material that was deposited as a liquid. However the features of claim 2 are advantageous, whereby the spacer is an elongated, preferably flexible, body offering manufacturing and cost advantages because being pre-manufacturable.

[0010] In this respect the features of claim 3 are especially pertinent, allowing simplified design to support and manufacture said loop.

[0011] The present invention is illustratively and schematically shown in the appended drawings.

[0012]FIG. 1 is an axial section of the distal end zone of an endoscope optics of the invention,

[0013]FIG. 2 is a front view perpendicularly to the window of the endoscope optics of FIG. 1, and

[0014]FIG. 3 is an elevation in the manner of FIG. 2 of an embodiment variation.

[0015]FIGS. 1 and 2 show the distal end zone of an endoscope fitted with an outer tube 1 conventionally made of an appropriate metal, further a window 2 made of an appropriate glass being inserted in sealing manner in the distal end of said tube 1, sealing illustratively being implemented by conventionally soldering the edges.

[0016] In the shown assembly, a system tube 3 rests inside the outer tube 2 and encloses an image transmitter in the form of the shown system of relay lens elements 4 and a distally mounted conventional objective lens 5. Again the conventional system tube 3 is made of an appropriate metal.

[0017] The residual inside cross-section of the outer tube 1 assumes a substantially half-moon shape (FIG. 2) on the outside and is filled with a light pipe in the form of an optic fiber bundle 6 terminating in a distal end face 7.

[0018] The opaque system tube 3 precludes light radiation within the outer tube 1 between the cross-sectional zone of the optic fiber bundle 6 and the cross-sectional zone of the image transmitter 4, 5. Accordingly the system tube 3 constitutes an opaque partition between the light pipe 6 and the image transmitter 4, 5.

[0019] By its distal edge 8, the system tube 3 acting as the partition abuts the window 2, namely by means of an insert which in this embodiment assumes the shape of an O-ring 9 that, as shown in FIGS. 1 and 2, runs annularly along the distal edge of the system tube 3. As shown in FIG. 1, the O-ring 9 of this embodiment rests in a groove in the end face of the edge of the system tube 3. In this embodiment the system tube 3 is appropriately thicker in its distal end zone.

[0020] The O-ring 9 is made of an elastic opaque material and rests at a given compression against the window 2 as shown by the annular surface 9 indicated by dashed lines. Illustratively the O-ring may be made of a black rubber.

[0021] When light exits the end face 7 of the optic fiber bundle 6, some of it will radiate laterally and therefore also will be reflected from the inside surface of the window 2. This light is incident on the gap between the system tube 3 and the window 2 and might pass through this gap to the objective lens 5 of the image transmitter. The O-ring 9 optically seals off this gap and precludes light penetration through the gap. The elastic O-ring 9 also assures that in the event of large thermal expansions of the system tube 3, the forces acting on the window 2 shall remain slight enough that destruction by thermal stress of said window need not be feared.

[0022] The shown optic-fiber bundle 6 also may be replaced by another light pipe, for instance a hose-like liquid light pipe, an acrylic bar or the like. Instead of the shown system of relay lens elements 4, 5, another image transmitter, for instance in the form of an optic fiber bundle, may be used—which illustratively need not be cross-sectionally circular. In this case the partition between image transmitter and light pipe then may assume shapes such as the tubular form shown in FIGS. 1 and 2. For instance the partition shape shown in FIG. 3 may the embodiment variant assuming the U-geometry 9′. As regards the array of relay lens elements 4, 5 shown in FIG. 1, the geometry shown in FIG. 3 may be present in the distal end zone whereas the system tube 3 shall be circular in the remaining region.

[0023] An insert other than the shown O-ring 9 also may be used between the distal edge of the system tube 3 or between another partition and the window 2, for instance in the form of an adhesive layer that was deposited in liquid form. The material used must be as opaque and elastic as possible in order to rest in well-sealing manner against the window 2. 

1. A rigid endoscope optics comprising an outer tube (1) of which the distal aperture is closed by a window (2) affixed to it in sealed manner, said outer tube enclosing an image transmitter (4, 5) running through it and a light pipe (6) running parallel to said transmitter, said transmitter and pipe being configured by their distal ends (5, 7) looking and resp. radiating through the window, the light-pipe's cross-section being separated from the image transmitter's cross-section at least in the region between their distal ends and the window by an optically opaque partition (3) that rests by its distal edge against the window, characterized in that the distal end of the partition (3) rests by means of an elastic and opaque insert (9) against the window (2).
 2. Endoscope as claimed in claim 1, characterized in that the insert is configured as a loop (9) to constitute an O-ring.
 3. Endoscope as claimed in claim 2, characterized in that the loop (9) rests in a groove constituted in the end face of the distal edge. 